Japanese laid-open patent publication No. 2013-173202 discloses a reciprocally rotating power tool which causes a cutting tool to reciprocally rotate in a transverse direction around an axis of a spindle by a motor. In this power tool, a crank shaft which is driven by the motor is provided. An eccentric shaft is provided on the crank shaft. The eccentric shaft is provided at a position displaced from an axial center of an output shaft of the motor which is a center of a rotation axis of the crank shaft.